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237 Cards in this Set
- Front
- Back
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Four types of chromosome mutations?
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Duplication, deletion, inversion, translocation
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Duplication
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Mutation that doubles a region of a chromosome
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Name the three types of chromosome duplicatons
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Tandem, Displaced, Reverse
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Tandem Duplication
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Type of duplication in which the duplicated region is immediately adjacent to the original segment. Ex. AB*CDEFGefg
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Displaced Duplication
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Type of duplication in which the duplicated region is located some distance from the original segment, either on the same chromosome or on a different one. EX. AB*CDEFGab
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Reverse Duplication
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A duplication in which the duplicated region is inverted. Ex. ABba*CDEFG
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Chromosome Deletions
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The loss of a chromosome segment
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Which is worse? A chromosome deletion or duplication?
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Chromosome deletion
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Chromosome Inversion
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A type of chromosome rearranpegement in which the segment is inverted (turned 180 degrees).
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Name the two types of chromosome inversion.
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Pericentric and Paracentric
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Inversion that does not include the centromere
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Paracentric Inversion
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Inversion that includes the centromere
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Pericentric Inversion
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AB*CDEFG to AB*CFEDG is an example of what type of chromosome rearrangement?
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Paracentric Inversion
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AB*CDEFG to ADC*BEFG is an example of what type of chromosome rearrangement?
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Pericentric Inversion
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AB*CDEFG to AB*CDEFGEFG is an example of what type of chromosome rearrangement?
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Tandem Duplication
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AB*CDEFG to AB*CDEFGAB is an example of what type of chromosome rearrangement?
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Displaced Duplication
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AB*CDEFG to ABBA*CDEFG is an example of what type of chromosome rearrangement?
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Reverse Duplication
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AB*CDEFG to AB*CDG is an example of what type of chromosome rearrangement?
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Chromosome Deletion
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Translocation
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The transfer or movement of genetic material between non-homologous chromosomes.
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How is translocation different from crossing over?
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Crossing over is the exchange of genetic material between homologous chromosomes while translocation involves the transfer or movement of genetic material between non-homologous chromosomes.
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Consider the following: AB*CDEFG and MN*OPQRS to AB*CDG and MN*OPEFQRS. What kind of chromosome arrangement has taken place?
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Nonreciprocal Translocation
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Consider the following: AB*CDEFG and MN*OPQRS to AB*CDQRG to MN*OPEFS. What kind of chromosome arrangement has taken place?
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Reciprocal Translocation
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Which chromosome mutations lead to a buckle called the deletion loop?
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Chromosome deletions and duplications lead to a buckle called the deletion loop.
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Which chromosome mutation leads to a spiral?
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Chromosome inversions lead to a spiral known as an inversion loop.
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At what phase during chromosome pairing would a deletion loop form? Inversion loop?
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Both the inversion and the deletion loop would form during prophase I of chromosome pairing.
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Which chromosome(s) and mutation type results in Chronic Myelogenous Leukemia.
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Chromosome 9 and 22, Reciprocal Translocation.
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Which chromosome(s) and mutation type results in Burkitt Lymphoma.
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Chromosome 8 and 14, Reciprocal Translocation
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A chromosome segment moves from one chromosome to a non-homologous chromosome or to another place on the same chromosome. This is an example of which type of chromosome rearrangement?
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Chromosome Translocation
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Why would "looping out" be observed during pairing in prophase I.
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"Looping out" allows the homologous sequence of the chromosomes to align if a mutation (such as chromosome duplication or deletion) would otherwise prevent this alignment from taking place.
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What would be the phenotypic consequence of a chromosome deletion if the deletion included the centromere?
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The chromosome would not segregate during meiosis or mitosis thus resulting in the lost of the chromosome.
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A chromatid that contains two centromeres is said to be?
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A dicentric chromatid.
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A chromatid that lacks a centromere is said to be?
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An acentric chromatid.
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Why would an acentric fragment (chromatid that lacks a centromere) be lossed during meiosis?
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The acentric fragment has no centromere thus the spindle fibers have no place to attach. The fragment does not segregate into a nucleus in meiosis and is usually lost.
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True or False. Recombinant progeny result when crossing over takes place within a paracentric inversion.
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False. NO recombinant progency result when crossing over takes place within a paracentric inversion.
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Consider an individual heterozygote for a paracentric inversion: Will a viable recombinant progeny result? Why or why not?
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Two of the gametes contain the original, nonrecombinant chromosomes. The other two gametes contain recombinant chromosomes that are missing some genes, these gametes will not go on to produce viable offspring. Thus, no recombinant progeny result when crossing over takes place within a paracentric inversion.
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Consider a heterozygous individual within a pericentric inversion: Will a viable recombinant progeny result? Why or why not?
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No viable recombinant progeny will result. The recombinant chromosomes either contain too many copies of some genes and/or no copies of other genes. Thus, gametes that receive the recombinant chromosomes can not produce viable progeny.
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Which type of inversion results in either a dicentric bridge or acentric chromatid?
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Paracentric Inversion
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What is a recombinant progeny?
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An offspring that contains a different combination of allels from either of it's parents.
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What is a dicentric bridge?
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A dicentric chromatid (contains two centromeres) that is stretched across the center of the nucleus during anaphase I of meiosis.
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Describes an outcome in which genes may be express differently depending on their positions.
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The position effect
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Consider a heterozygous individual for an inversion: Will an inversion loop arise? Why or Why not?
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The gene order of the two homologs differs, and the homologous sequence can align and pair only if the two chromosomes form an inversion loop.
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Consider a homozygous individual for an inversion: Will an inversion loop arise? Why or why not?
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The two homologous chromosomes can pair and separate normally. No inversion loop is expected to arise.
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Consider a homozygous and a heterozygous individual for an inversion: Which would be more likly to produce non viable progeny?
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Individuals heterozygous for an inversion are more likely to produce gametes that are non viable.
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Paracentric inversions lead nonviable, abnormal gametes. Why?
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The resulting recombinant gametes are nonviable because they are missing some genes.
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Pericentric inversions lead to nonviable, abnormal gametes. Why?
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The resulting recombinant gametes are nonviable because they are missing some genes and/or too many genes are present.
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When does the effect of translocation on chromosome take place in meiosis?
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Anaphase I
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Which type of chromosome rearrangement may result in the chromosomes segregating in three different ways.
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Chromosome Translocation
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Consider a homozygous and a heterozygous individual for an inversion: Which would be more likly to produce non viable progeny?
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Individuals heterozygous for an inversion are more likely to produce gametes that are non viable.
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Paracentric inversions lead nonviable, abnormal gametes. Why?
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The resulting recombinant gametes are nonviable because they are missing some genes.
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Pericentric inversions lead to nonviable, abnormal gametes. Why?
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The resulting recombinant gametes are nonviable because they are missing some genes and/or too many genes are present.
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When does the effect of translocation on chromosome take place in meiosis?
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Anaphase I
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Which type of chromosome rearrangement may result in the chromosomes segregating in three different ways.
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Reciprocal Translocation
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Of the three products of segregation, which produces viable gametes? Why?
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The gametes produced by alternate segregation posses one complete set of the chromosome segments. These gametes are therefore functional and can produce viable progeny.
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Of the three products of segregation, which produces nonviable gametes? Why?
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The gametes produced by adjacent-1 and adjacent-2 segregation are not viable. This is because some chromosome segments are present in two copies, whereas others are missing.
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Of the three products of segregation, which type(s) of segregation is considered rare?
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Adjacent-2 segregation is considered rare.
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Of the three products of segregation, which type(s) of segregation occur most frequently?
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Most gametes are produced by alternate or adjacent-1 segregation.
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Approximately how many gametes are expected to be functional from an individual heterozygous for a reciprocal translocation.
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Approximately half.
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Which type of chromosome rearrangement (mutation) accomplishes crossing over?
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All.
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True or False. Deletions frequently accompanys translocations?
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True
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The short arm of one acrocentric chromosome is exchanged with the long arm of another. This describes this kind of translocation.
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Robertsonian Translocation.
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What does a robertsonian translocation generate?
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A robertsonian translocation generates a metacentric chromosome with two long arms and another chromosome with two very short arms.
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True or False. During a robertsonian translocation the larger chromosome often fails to segregate resulting in an over all gain in chromosome numbers.
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False. During a robertsonian translocation, a metacentric chromosome with two long arms and another chromosome with two short arms is generated. The chromosome with the two short arms often fails to segregate and is lost. This leads to an overall reduction in the number of chromosomes.
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True or False. Crossing over can not occur within an inversion loop.
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False. Crossing over does occur within an inversion loop.
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True or False. A chromosome lacking a centromere is normally lost.
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True.
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How can chromosome inversions produce viable recombinant progeny?
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Some viable recombinant progeny may be produced through two-stranded double crossovers.
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True or False. Individual organisms with inversions have gained genetic material.
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False. Individual organisms with inversions have neither lost or gained genetic material. However, the gene ordered is altered. This results in the loss of genetic material during prophase I of meiosis producing nonviable recombinant progeny and pronounced phenotypic effects.
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A change in the number of individual chromosomes.
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Aneuploidy
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A change in the number of chromosome sets.
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Polyploidy
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Down's Syndrome is the result of what type of chromosome number variation? Aneuploidy or Polyploidy?
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Aneuploidy
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Triploid is the result of what type of chromosome number variation? Aneuploidy or Polyploidy?
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Polyploidy
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Trisomy 21 is the result of what type of chromosome number variation? Aneuploidy or Polyploidy?
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Aneuploidy
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Type of anueploidy that results in the loss of both members of a homologous pair (2n-2)
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Nullisomy
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Type of aneuploidy that results in the loss of one member of a homologous pair (2n-1).
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Monosomy
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Type of aneuploidy that results in the gain of a single chromosome (2n+1).
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Trisomy
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Type of aneuploidy that results in the gain of a pair of homologous chromosomes (2n+2).
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Tetrasomy
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What is the only viable monosomy in humans? What disease does it produce?
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XO, Turner Syndrome
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True or False. Most trisomies are lethal?
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True.
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Why is triplo-x (xxx) and kleinfelter's syndrome (xxy) viable?
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The extra X's are inactivated.
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True or False. Trisomy 13 and 18 are rare and lethal by age 3.
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True.
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Trisomies are the result of what?
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Trisomies result from the failure of chromosomes to separate. This is known are nondisjunction.
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Familial down syndrome arises in offspring whose parents are carriers of chromosomes that have undergone this and between which two chromosomes.
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A robertsonian translocation between chromosome 21 and 14
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True or False. Persons whom are translocation carriers have downs syndrome.
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False.
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Type of polyploidy in which all chromosome sets are from a single species
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Autopolyploidy
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Type of polyploidy in which chromosome sets are from two or more species.
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Allopolyploidy
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Type of polyploidy that results from the hybridization of two species
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Allopolyploidy
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Type of polyploidy that results from chromosome duplication within a species.
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Autopolyploidy
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True or False. Polyploidy in plants are derived from the hybridization events between closely related species.
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True.
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Consider genetic material: Why is "coding" a criteria?
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The genetic material must be capable of storing large amounts of information in a stable form.
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Consider genetic material: Why is "replication" a criteria?
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The genetic material must have the capacity to be copied accurately.
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Consider genetic material: Why is "expression" a criteria?
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The genetic material (genotype) must have the capacity to "code for" (determine) traits (the phenotype).
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Consider genetic material: Why is "mutation" a criteria?
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The genetic material must be changeable to allow organisms to adapt to their environment.
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True or False. Chromosomes contain both DNA and proteins.
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True.
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How many amino acids are proteins composed of?
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20
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How many nucleotides is DNA composed of?
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4
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What did Griffith's experiment demonstrate?
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Griffith's experiment demonstrated transformation in bacteria (Streptococcus pneumoniae).
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Describe Griffith's experiment.
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A small amount of living type IIR bacteria (rough S. pneumoniae, non-virulent) was injected into a mouse along with a large amount of heat-killed IIIS bacteria (smooth S. pneumoniae, non-virulent) which are normally virulent when alive. Five days later, after the injection, the mice died of pneumoniae. Examining the blood of the mice, Griffith found live type IIIS virulent bacteria. Griffith concluded the type IIR bacteria had mutated to the virulent S form, acquiring the genetic virulence of the dead type IIIS bacteria.
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Describe "Avery, MacLeod, McCarty" experiment.
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Repeated Griffith's experiment, but treated the heat-killed S bacteria with enzymes before mixing with the live R bacteria. Cultures treated with protease or RNase contained the transformed IIIS virulent bacteria. However, the culture treated with DNase does not.
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What did "Avery, MacLeod, McCarty" experiment demonstrate?
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Avery, MacLoed and McCarty demonstrated that the transforming principle is DNA, providing the first evidence that DNA is the genetic material.
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Describe the Hershey-Chase experiment.
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Using radioactive isotopes, they traced the movement of DNA and protein during phage reproduction. They found although the protein component of a phage is necessary for infection, it does not enter the cell and is not transmitted to progeny phages.
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What did the Hershey-Chase experiment demonstrate?
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The Hershey-Chase experiment demonstrated that DNA carries the genetic information in bacteriophages
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Consider the Hershey-Chase experiment: What was used as a radioactive isotope label for DNA? What about protein?
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32-Phosphorous was used for DNA and 35-Sulfur was used for protein. DNA did not contain sulfur and protein did not contain phosphorous so these elements were ideal to use.
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What did Hershey-Chase experiment confirm about DNA and protein?
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The results from the Hershey-Chase experiment confirmed that DNA, not protein, is the genetic material of the phages.
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Who solved the 3-D structure of DNA?
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Watson and Crick
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What does each nucleotide consist of?
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A five-carbon sugar, one or more phosphate groups, and a cyclic nitrogenous base.
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What is the difference between a ribose and a deoxyribose sugar?
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The 2' carbon of a ribose sugar carries a hydrogen and hydroxyl group while the 2' carbon of a deoxyribose sugar carries two hydrogens.
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When determining the orientation of the five-carbon sugar, the 5' carbon with HOCH2 should be in what direction.
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Top left side.
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Phosphates are found in DNA or RNA?
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Phosphates are found in both DNA and RNA.
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What kind of charge does a phosphate molecule express?
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Phosphates are highly negatively charged.
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Would a phosphate molecule be hydrophobic or hydrophilic?
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Due to the high negative charge of a phosphate molecule, they are hydrophilic (water-loving).
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What part of the nucleotide structure is rich in energy?
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The phosphate group is energy-rich.
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Purines? List the nitrogenous bases.
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Adenine and Guanine
(Pure As Gold) |
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Pyrimidine? List the nitrogenous bases.
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Cytosine, Thymine, and Uracil.
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Which nitrogenous base is only present in RNA?
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Uracil
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Which nitrogenous base is only present in DNA?
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Thymine
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What is the structural difference between thymine and uracil?
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Thymine has a methyl group attached to the 5'-carbon. Uracil has a -CH attached to the 5'-carbon.
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How many chemically distinct nucleotides are used to build DNA and RNA?
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8
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Describe the deoxyribonucleotide structure. Which end carries the phosphate? Hydroxyl group?
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Starting on the deoxyribose sugar: The 1' carbon carries the nitrogenous base, the 5' end carries phosphate (5'-PO4), and the 3' carbon has a free hydroxyl group (3'-OH).
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Which nitrogenous base does dAMP contain?
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Adenosine
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What does dTMP stand for?
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Deoxythymidine 5'-monophosphate
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What molecule facilitates the reaction used to build polynucleotides? How (briefly)?
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Nucleoside triphosphates, the liberation of the extra phosphates provides the needed energy.
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What reaction facilitates the building of polynucleotides?
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Nucleotides are joined by a dehydration reaction between the 3'OH of the last nucleotide and the 5'-phosphate of the next nucleotide. The result is a phosphodiester bond.
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The backbone of a polynucleotide is composed of what?
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Repeating phosphate-sugar units
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Which nitrogenous base pairs with Adenine?
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Thymine
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True or False. Purines pair with purines.
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False. Purines pair with pyrimidines.
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Which nitrogenous base pairs with Guanine?
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Cytosine
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Which nitrogenous base pairs with Cytosine?
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Guanine
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Which nitrogenous base pairs with Thymine?
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Adenine
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True or False. The total concentration of Adenine and Thymine equals the total concentration of Purines.
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False. The total concentration of purines (A+G) equals the total concentration of pyrimidines (C+T).
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DNA was extracted from cells of S. afermentans and analyzed for base composition. It was found that 34% of the bases are Thymine. With this information, predict what percentage of the bases are Guanine.
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66%, (100-34).
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On the double helix, which direction does the phosphates face?
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Outward
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On the double helix, which direction do the bases face? What do they pair with?
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The bases are inside the double helix and pair with hydrogen bonds.
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Consider a double helix: How do the two strands pair?
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There are two anti-parallel strands that form the double helix.
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Who figured out how the nitrogenous bases are paired? What tool was used?
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Watson and Crick, X-ray crystalograhy.
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What force holds two polynucleotide chains together?
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Hydrogen bonding
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How many hydrogen bonds holds cytosine and guanine together? Adenine and thymine?
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3, 2.
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True or False. The sugar-phosphate backbone runs antiparallel.
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True.
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Which form of DNA is most common?
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The B form.
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Which DNA form is rich in Guanine and Cytosine?
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The Z form.
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Of the three helix forms, which is left-handed?
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The Z form.
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Of the three helix forms, which is right-handed?
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The A and B forms.
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How many base pairs are in a turn of the B helix form?
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10
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True or False. The helix A form is mostly likely found in the cells.
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False. It is almost never found in the cells.
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Which helix form is mostly H2O?
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The helix B form.
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How many polynucleotide strands does a DNA molecule contain?
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Two.
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True or False. The polynucleotides strands are identical to one another.
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False. The two polynucleotide strands are complementary and antiparallel to one another.
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What is Chargaff's rule?
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The total amount of adenine is always equal to the amount of thymine (A+T), and the amount of guanine is always equal to the amount of cytosine (G=C).
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Describe the flow of genetic information (central dogma of biology).
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DNA replication, transcription, RNA, translation, protein
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List the three levels of a DNA structure.
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Primary, Secondary, and Tertiary
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Describe the primary structure of a DNA molecule.
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The primary structure is simply the nucleotide squence.
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Describe the secondary structure of a DNA molecule.
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The secondary structure is the double-helical structure.
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Describe the tertiary structure of a DNA molecule.
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The tertiary structure rfers to higher order folding that allows DNA to be packed into the confined space of a cell
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Which direction does B-DNA twist? This is an example of what type of supercoiling?
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B-DNA twists to the left and is the result of negative supercoiling.
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True or False. Bacterial DNA is linear.
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False. Bacterial DNA is circular. It has no free ends.
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Consider bacterial: one circular chromosome equals how many DNA molecules?
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One circular chromosome equals one DNA molecule.
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In which form is the DNA significantly longer? Relaxed or Supercoiled?
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Relaxed.
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Supercoiling?
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A type of DNA tertiary structure in which the DNA helix is subjected to strain by being under or over wound.
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How many base turns will yield the lowest energy state for B-DNA?
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Supercoiling of 10 bases per turn.
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True or False. Eukaryotic chromosomes contain circular DNA.
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False. Eukaryotic chromosomes each contain one linear DNA molecule.
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What are the two types of chromatin?
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Euchromatin and heterochromatin.
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Euchromatin?
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Type of chromatin that undergoes the normal process of condensation and decondensation in the cell cycle.
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Heterochromatin?
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Type of chromatin that remains in a highly condensed state throughout the cell cycle, even during interphase.
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Chromatin?
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Material found in the eukaryotic nucleus, consists of DNA and proteins.
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True or False. Chromatin is found in both eukaryotic and bacterial cells?
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False. Chromatin is only found in eukaryotic cells.
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Name the most abundant proteins in chromatin?
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Histones
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DNA is complexed with histones to form this structure.
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Nucleosomes.
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Nucleosome?
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A core particle consisting of DNA wrapped about two times around an octamer of either hisone proteins. This resembles thread around a spool.
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Solenoids?
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Supercoiled nucleosomes.
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Chromosomal scaffold protein?
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A chromosomal protein "skeleton" in which histones and other chromosomal proteins are removed (usually with a high salt concentrated solution). Scaffold proteins may help fold and pack chromosomes.
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Describe the "multiple levels" of eukaryotic DNA packing.
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1. DNA is wrapped into a nucleosome.
2. The nucleosomes are then supercoiled to form solenoids. 3. Solenoids form loops on a nonhistone scaffold. 4. Loops are condensed into chromatin fibers. |
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Linker DNA?
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DNA comprised of approximately 30 to 40 base pairs. A strip of DNA between nucleosome cores which hold them together.
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What charge do histones have?
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Very basic proteins, have a negative charge.
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True or False. Histones may play a role in activating or silencing regions of RNA?
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False. Histones may play a role in activating or silencing DNA.
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List the five histone proteins. Which are found inside? Outside?
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H1 (outside complex). H2a, H2b, H3, H4 (inside complex).
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How much DNA is in direct contact with the histone octamer?
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Between 145-147 base pairs in length.
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True or False. Is the DNA wrapped around a histone supercoiled?
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True.
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Complex plus linker = nucleosome. How many base pairs of DNA?
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Approximately 167 bases pairs in length.
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Which histone protein allows nucleosomes to become compacted?
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Histone H1.
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"bead on a string" form of chromatin?
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Nucleosome
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30-nm chromatin fiber of packed nucleosomes?
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Solenoid
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Section of chromosome in extended form?
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Loops
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Condensed section of chromsomes?
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Fibers.
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Centromere?
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A constricted region of the chromsomes to which spindle fibers attach and is essential for proper chromosome movement in mitosis and meiosis.
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True or False. The centromere consists of a particular sequence repeating many times.
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True.
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What part of the centromere codes for a protein?
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No part of the centromeric sequence codes for a protein. The centromere is an attachment site for proteins.
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The centromere is the binding site for what complex?
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The centromere is the binding site for the kinetochore complex.
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Why would chromosomes without centromeres be lost in mitosis?
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During mitosis, the spindle fibers attach to the kinetochore of the centromere and orient the chromosomes on the metaphase plate. If anaphase is initiated before each chromosome is attached to the spindle fibers, chromosomes will not move toward the spindle pole and will be lost.
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Telomeres?
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Serves as a cap that stabilizes the chromosome.
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True or False. The centromere consists of a particular sequence repeating many times.
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True.
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What part of the centromere codes for a protein?
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No part of the centromeric sequence codes for a protein. The centromere is an attachment site for proteins.
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The centromere is the binding site for what complex?
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The centromere is the binding site for the kinetochore complex.
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Why would chromosomes without centromeres be lost in mitosis?
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During mitosis, the spindle fibers attach to the kinetochore of the centromere and orient the chromosomes on the metaphase plate. If anaphase is initiated before each chromosome is attached to the spindle fibers, chromosomes will not move toward the spindle pole and will be lost.
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Telomeres?
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Telomeres protect the ends of the DNA molecule from unraveling or degrading. Also, telomeres prevent the fusion of the ends of one chromosome to another.
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Which type of supercoiling is more common?
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Negative supercoiling.
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The double helix wraps around and forms a figure 8 due to the tension present.
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Supercoiling.
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What is the structural diameter of DNA?
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2 nm
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What is the structural diameter of nucleosomes?
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11 nm
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What is the structural diameter of solenoids?
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30 nm
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What is the structural diameter of loops?
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300 nm
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What is the structural diameter of chromatids?
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700 nm
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List the levels of chromatin organization from smallest to largest: Loops, Nucleosome, DNA, Solenoid, Chromatid.
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DNA, Nucleosome, Solenoid, Loops, Chromatid
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What does the nucleosome structure consist of?
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The nucleosome include the bead and it's DNA linker. The "bead" is the nucleosome core. It consists of 8 histone proteins. The DNA wraps around the bead 1.65 times.
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Chromatosome?
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The core nucleosome particle and its associated H1 histone protein.
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Approximately how many base pairs of DNA is wrapped around the nucleosome "bead"?
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145-147 base pairs of DNA.
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How many base pairs of DNA total per nucleosome complex?
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Approximately 167 bp of DNA are held within the chromatosome (DNA wrapped around nucleosome "bead" plus DNA attached to H1 protein which range between 20 to 22 bp), plus 30 to 40 bp connecting each chromatosome totaling approximately 200 bp all together per nucleosome complex.
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H1 histone protein is bound to what part of the chromatin complex?
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H1 Histone protein is bound to the linker DNA. It is not part of the histone octamer.
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Consider the following:
5'-CCCTAA 3'GGGATT Which direction would you expect the end of the is chromosome to be oriented? |
The sequence is always oriented with the string of C's and G's toward the end of the chromosome. This is the repeating unit in human telomeres.
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Consider the following telomeric sequence:
_______5'CCCTACCCTA 3'GGGATGGGATGGGAT Why does the G-rich strand protrude beyond the complementary C-rich strand at the end of the chromsomes? What is called? |
Special POT (protecetion of telomere) proteins bind to the G-rich single-stranded sequence, protecting the telomere from degradation and preventing the ends of chromosomes from sticking together.
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How can telomeres be labeled?
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Telomeres can be labeled by targeting the repeat sequence.
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How many H2A, H2B, H3 and H4 phistone proteins are in each nucleosome?
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2
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Have many H1 histone proteins are associated with each nucleosome?
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1
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DNA is built is which direction? The template strand is read in which direction?
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DNA chains are built in the 5' to 3' direction. The template chain is read in the 3' to 5' direction.
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What are the three models of replication?
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Conservative, Semi-conservative, and Disperisve.
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Conservative DNA replication?
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The entire double-stranded DNA molecule serves as a template for a whole new molecule of DNA. The original DNA molecule is fully conserved during replication.
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Dispersive DNA replication?
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Both nucleotide strands break down into fragments, which serve as templates for the synthesis of new DNA fragments. In this model, each resulting DNA molecule is interspersed with fragments of old and new DNA. None of the original molecule is conserved.
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Semi-conservative DNA replication?
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Each strand serves as a template for a new DNA molecule. Each of the original DNA molecules remain intact despite no longer being combinded to the same molecule.
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Which mechanism of replication is used?
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Semi-conservative.
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Describe Meselen and Stahl experiment.
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Used equilibrium density gradients centrifugation to distinguish between old and new DNA. Used two nitrogen isotopes. Determined which of the three replication models is used.
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What did Meselson and Stahl determine?
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Meselson and Stahl demonstrated that replication in E. coli is semiconservative. The products of replication are one old chain paired with one fully new chain.
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Theta replication?
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Common type of replication that takes place in circular DNA (such as E. coli). Generates a structure that resembles the greek letter theta. Double-stranded DNA unwinds at replication origin, single-stranded nucleotides are produced, these serve as templates on which new DNA can be synthesized.
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Rolling-circle replication?
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Takes place in some viruses in E. coli. Is initiated by a break in one of the nucleotides strands that creates a 3' OH groups and a 5' phosphate group. Here, new nucleotides are added to the 3' end of the broken strand, with the inner (unbroken) strand used as a template.
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True or False. Eukaryotes use linear DNA replication?
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True.
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Replicon?
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A unit of DNA that is replicated.
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Consider bacteria and viruses chromosomes: One origin equates to how many replicons?
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one replicon equates to one origin bubble.
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Consider eukaryotic chromosomes: Many origins equates to how many replicons?
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Many origins equates to many replicons.
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In which direction does replication occur in E. coli?
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Replication is bidirectional in E. coli.
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How many origin of replications may a linear chromosome have?
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Multiple origin of replications.
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Which end of a DNA strand consists of a phosphate molecule? Can a dNTP molecule attach at this end?
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The 5' end of a DNA strand consists of the phosphate molecule (5' PO4). A phosphodiester bond can not form at this location with the dNTP molecule. A reaction can not take place since a phosphate is already attached at the 5' end, the triphosphate molecule (on the dNTP) has no way of breaking to release energy.
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In which direction is the DNA molecule READ?
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3' to 5'
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In which direction is the DNA molecule BUILT?
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5' to 3'
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Which DNA strand is discontinuous?
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The lagging strand.
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Which DNA strand contains the okazaki fragments?
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The lagging strand.
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Which DNA strand is continuous?
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The leading strand.
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How is the dsDNA helix unzipped?
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DNA helicases unwind the DNA
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DNA topoisomerases?
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Cleaves the phophodiester bond so the helix can swing around as it unwinds.
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Of the two classes of topoisomerases, which requires ATP?
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Topoisomerase II requires ATP, it breaks and reforms the phosphodiester bonds on TWO strands at once.
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What is released after the 5'-PO4 of the dNTP is added onto the 3'-OH end of the DNA molecule.
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Phosphate is released
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Replication fork?
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Unwound region that is being replicated.
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